1- Calculate the percent by mass of potassium nitrate in a solution made from 45.0 g KNO₃ and 295 mL of water. Density of water is 0.997 g/mL A. 1.51% B. 7.57% C. 13.3% D. 15.2% E. none of them 2- How many grams of water are needed to dissolve 27.8 g of ammonium nitrate NH₄NO₃ in order to prepare a 0.452 m solution ? A. 0.157 g B. 36.2 g C. 100 g D. 769 g E. 157 g 3- In how many grams of water should 25.31 g of potassium nitrate (KNO₃) be dissolved to prepare a 0.1982 m solution ? A. 250.0 g B.792 g C.1000 g D. 1263 g E. 7917 g 4- The solubility of gases in water usually decreases with : A. increased pressure . B. increased temperature . C. decreased temperature . 5- The solubility of nitrogen gas at 25°C and 522 mm Hg is 4.7x10¯⁴ mol/L .What is the value of Henry’s Law constant in mol/L atm ? A. 6.8 x 10¯⁴ mol/L atm B. 4.7 x 10¯⁴ mol/L atm C. 3.2 x 10¯⁴ mol/L atm D. 9.0 x 10¯⁷ mol/L atm E. 1.5 x 10³ mol/L atm 6- The solubility of CO₂ gas in water : A. increases with increasing temperature . B. decreases with decreasing temperature . C. decreases with increasing temperature . D. is not dependent on temperature . 12.24 According to Raoult’s law , which statement is false ? A. the vapor pressure of a solvent over a solution decreases as its mole fraction increases . B. the solubility of a gas increases as the temperature decreases . C. the vapor pressure of a solvent over a solution is less than that of pure solvent . D. the greater the pressure of a gas over a solution the greater its solubility . E. ionic solutes dissociate in solution causing an enhancement of all colligative properties . 12.27 Dissolving a solute such as KOH in a solvent such as water results in : A. an increase in the melting point of the liquid . B. an decrease in the boiling point of the liquid . C. an decrease in the vapor pressure of the liquid . D. no change in the boiling point of the liquid . 12.29 Which of the following aqueous solution has the highest boiling point ? Given K=0.52°C/m. A. 0.2m KCI B. 0.2 m Na₂SO₄ C. 0.2 m Ca(NO₃)₂ D. pure water . E. more than one of the above .